In drilling or production of an offshore well, risers extend between a vessel or platform at the surface and a subsea wellhead thereby connecting the vessel or platform to the subsea wellhead. In certain implementations, the riser may couple the subsea wellhead to a Blow-Out-Preventer (“BOP”) located at the surface. The riser may be as long as several thousand feet, and may be made up of successive riser sections that are coupled together through one or more riser connections. Riser sections with adjacent ends may be connected on board the vessel or platform, as the riser is lowered into position. Auxiliary lines, such as choke, kill, and/or boost lines, may extend along the side of the riser to connect with the wellhead, so that fluids may be circulated downwardly into the wellhead for various purposes.
It is often desirable to use a riser which has a small inner diameter in order to facilitate fluid flow at higher pressures. For instance, during drilling operations it may be desirable to use a dual riser with an inner riser section that has a small inner diameter in order to provide a higher pressure capacity and improve the hydraulic circulation of the drilling fluid (mud) from the subsea wellhead to the surface. Stated otherwise, using a riser with a smaller diameter allows the fluids to be directed uphole at a higher velocity and with a higher pressure. In certain implementations, the smaller riser may reside inside a larger, lower pressure rated riser. It is therefore desirable to develop a tie-back connector that can couple a small diameter riser to a subsea wellhead.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.